Four Japan-based U.S. service members were injured on Thursday following a negligent discharge of a firearm that occurred at Camp Schwab in northeast Okinawa. (Kazuhiro Nogi / AFP)

Four Japan-based U.S. service members were injured on Thursday following a negligent discharge of a firearm that occurred at a Marine Corps base in northeast Okinawa.

All four troops are in stable condition with no major injuries to report following the incident. The discharge occurred aboard Camp Schwab, home to the 4th Marine Regiment, at approximately 10:45 Thursday morning, said 2nd Lt. Courtney Caimona, a spokeswoman for III Marine Expeditionary Force, based in Okinawa.

“There exists no evidence at this time to indicate this was an intentional shooting, or a result of anything other than negligence,” she said.

It’s not immediately clear what kind of weapon was discharged. It’s also unclear if the four injured aboard the Marine Corps base were Marines, or included members of other services. Caimona declined to provide the names of those involved, their ranks or units because the incident remains under an ongoing investigation.

The negligent discharge was initially reported to the Marine Corps Provost Marshal’s Office, Caimona said. The Naval Criminal Investigative Service is currently investigating the incident, she added.